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Giardiasis- Causes, Transmission, Treatment and Prevention

Definition

Giardiasis (giardia) is an intestinal infection marked by abdominal cramps, bloating, nausea, and bouts of watery diarrhea. Giardia infection is caused by Giardia lamblia a microscopic parasite that is found worldwide, especially in areas with poor sanitation and unsafe water. Infection with giardiasis is one of the most common causes of waterborne disease in the USA. The parasites are found in streams and lakes in the backcountry but also in municipal water supplies, pools, whirlpool spas, and wells. Infection with giardia may be transmitted through food and contact person to person.

Infections of the Giardia typically clear up within weeks. But you may have bowel problems long after the parasites have gone away. Several drugs are generally effective against parasites of giardia but not all respond to them. Prevention is the best defense for you.

Life cycle

The parasite has a direct life cycle. It lives in the lower small intestine of the cat in its trophozoite form, adherent to the intestinal wall. It replicates by binary fission to produce the encysted form, which is passed in the feces in addition to the trophozoites.

Life cycle of Giardia lamblia

Spread of Giardiasis

Giardiasis can be spread by:

Anything that comes into contact with feces (poop) from infected humans or animals can become contaminated with the Giardia parasite. People become infected when they swallow the parasite. It is not possible to become infected through contact with blood.

Epidemiology

Giardia has a worldwide distribution, occurring in both temperate and tropical regions. It continues to be the most frequently identified human protozoal enteropathogen. Prevalence rates vary from 4-42%. In the industrialized world, overall prevalence rates are 2-5%. In the developing world, G intestinalis infects infants early in life and is a major cause of epidemic childhood diarrhea. Prevalence rates of 15-20% in children younger than 10 years are common.

Giardia is the most common gut parasite in the United Kingdom, and infection rates are especially high in Eastern Europe. Prevalence rates of 0.94-4.66% and 2.41-10.99% have been reported in Italy.

Giardiasis risk factors

Giardiasis is more common in places with poor water or sewage treatment. Asia and South America have the highest infection rates. Risk is also higher for people who:

Causes of Giardiasis

The parasite that causes giardiasis lives in 2 stages:

The infection starts when the cysts are taken in through contaminated food or water. Stomach acid activates the cysts and the trophozoites are released. They attach to the lining of the small intestine and reproduce. Cysts form in the lower intestines. They are then passed in the feces.

The parasite may be passed from person-to-person by contact with infected feces, or through consuming contaminated food or water.

Symptoms

More than two-thirds of people who are infected may have no signs or symptoms of illness, even though the parasite is living in their intestines. When the parasite does cause symptoms, the illness usually begins with severe watery diarrhea, without blood or mucus. Giardiasis affects the body’s ability to absorb fats from the diet, so diarrhea contains unabsorbed fats. That means that the diarrhea floats is shiny, and smells very bad.

Other symptoms include:

These symptoms may last for 5 to 7 days or longer. If they last longer, a child may lose weight or show other signs of poor nutrition.

Sometimes, after acute (or short-term) symptoms of giardiasis pass, the disease begins a chronic (or more prolonged) phase. Symptoms of chronic giardiasis include:

Complications            

These complications can occur:

Diagnosis and test

Giardia infection can be challenging to diagnose; Health care providers rely on a stool analysis to confirm the presence of the parasite.

Stool Analysis

Checking your stool for the parasite is the primary way doctors diagnose a Giardia infection. The test can be done in one of two ways, both of which will require you to provide a stool sample.

Stool Ova and Parasites Exam: For this exam, a small amount of stool is smeared on a slide. The sample is examined with a microscope for signs of cysts or adult parasites.

Antigen Test: An antigen test doesn’t look for the whole parasite—rather, it looks for a protein made by Giardia when it’s in the human body.11 These proteins are what the immune system responds to when it’s trying to defend itself from the infection.

Giardia parasites can be hard to spot and don’t always show up in a stool sample from someone who is infected. If your doctor suspects you have giardiasis, they might order both tests at the same time. Or, if the first test comes back negative, they might have you give additional stool samples especially if your symptoms match up with giardiasis.

String Test

If stool tests don’t confirm the diagnosis but your doctor still suspects giardiasis, they might use another tool called the string test or Entero-test.

Treatment and medications

Children and adults who have giardia infection without symptoms usually don’t need treatment unless they’re likely to spread the parasites. Many people who do have problems often get better on their own in a few weeks.

When signs and symptoms are severe or the infection persists, doctors usually treat giardiasis with medications such as:

Metronidazole (Flagyl): Metronidazole is the most commonly used antibiotic for giardia infection. Side effects may include nausea and a metallic taste in the mouth. Don’t drink alcohol while taking this medication.

Tinidazole (Tindamax): Tinidazole works as well as metronidazole and has many of the same side effects, but it can be given in a single dose.

Nitazoxanide (Alinia): Because it comes in a liquid form, nitazoxanide may be easier for children to swallow. Side effects may include nausea, flatulence, yellow eyes, and brightly colored yellow urine.

There are no consistently recommended medications for giardiasis in pregnancy because of the potential for adverse drug effects on the baby. If your symptoms are mild, your doctor may recommend delaying treatment until after the first trimester. If treatment is necessary, discuss the best available treatment option with your doctor.

Prevention of Giardiasis

To help prevent the spread of giardia:

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